Embodiments of the present invention relate to components used in the transportation and support of substrates in process chambers.
In the fabrication of semiconductors and displays, material is formed or deposited on a substrate, such as a semiconductor wafer or dielectric, by processes such as chemical vapor deposition (CVD), physical vapor deposition (PVD), ion implantation, oxidation and nitridation. The material formed on the substrate can also be etched to define features of electric circuits and devices. Such processes are generally performed in a process chamber in which a plasma may be generated. The substrate is transported from a cassette in a load-lock or transfer chamber to the process chamber on a robot blade. The transported substrate is placed on a set of lift pins that are lowered though holes in a substrate support to rest the substrate on the support. The substrate support often includes a pedestal, vacuum chuck having a vacuum port to suck down the substrate, or an electrostatic chuck comprising a dielectric covering an electrode to which a voltage is applied to generate an electrostatic force to hold the substrate. The chamber has enclosure walls about the substrate support, a gas distributor and exhaust, and a gas energizer.
During the transportation and support of the substrate, various support surfaces come in contact with the backside of the substrate, for example, the robot blade that contacts the substrate backside, the lift pin contact regions, and the receiving surface of the substrate support. Several other surfaces can also contact the substrate. For example, in some processes, the substrate is initially transported to a degassing heater plate on which it is rested to degas the substrate. The substrate may also be transferred to a cool-down pedestal to cool the substrate after rapid thermal processing or other high temperature processes. Shutter disks can also be provided to protect the surfaces of substrate supports when the substrate is not being held on the support.
The surfaces that contact the backside of the substrate can cause contaminants and residual matter to remain on the substrate. For example, stainless steel surfaces of a substrate support pedestal, cool down plate, or degas heater, can leave behind trace amounts of iron, chromium or copper on the back surfaces of the substrate. Nickel coated robotic blades could also leave residual nickel contaminant on the substrate when they are used to lift and transport the substrate. Similarly, aluminum pedestals can also leave behind small aluminum particles on the substrate. Shutter disks can contaminate the top surface of pedestal supports, with the contamination being transferred to the substrate when the substrate is placed on the pedestal support. While these contaminants are initially deposited on the inactive backside of the substrate, they diffuse into the active front side in subsequent high temperature annealing processes, causing shorts or failure of the circuits or displays of the substrate. The contaminants can also flake off from the substrate fall upon and contaminate other substrates. These contaminants eventually cause shorts in the electrical circuits of the substrate reducing the effective yields of circuits or displays obtained from the substrate. Thus, it is desirable to reduce contamination of the backside of the substrate to increase substrate yields.